Reversible fiber optic stub clamping mechanism

ABSTRACT

A fiber optic stub fiber connector for reversibly and nondestructively terminating an inserted field fiber having a buffer over at least a portion thereof. The connector includes a housing and a ferrule including a stub fiber disposed within and extending from a bore through the ferrule. The ferrule is generally at least partially disposed within and supported by the housing. The connector further includes a reversible actuator for reversibly and nondestructively terminating the inserted field fiber to the stub fiber. The reversible actuator includes a buffer clamp for engaging with the buffer to simultaneously provide reversible and nondestructive strain relief to the terminated field fiber.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/328,947, filed on Jan. 10, 2006, entitled “Reversible Fiber OpticStub Fiber Clamping Mechanism” which is a continuation of U.S. patentapplication Ser. No. 10/647,848, filed on Aug. 25, 2003, entitled“Reversible Fiber Optic Stub Fiber Connector.”

BACKGROUND OF THE INVENTION

Fiber optic networks are becoming increasingly commonplace intelecommunications applications due to their increased bandwidth anddistance capabilities relative to copper networks. Compared to coppersystems, however, fiber optic cables and connections are well-known fortheir more critical and difficult terminations. For example, thealignment between abutted glass cores within a fiber optic interface iscrucial to the performance of the connection.

Field installation of standard “pot and polish” fiber optic connectorsis extremely labor-and expertise-intensive. The installer is required toprepare a fiber end, glue the fiber end into the connector, cleave theexcess fiber from the endface of the connector, and polish the endfaceof the connector to obtain the optimum geometry for optical performance.Endface polishing is a difficult and time-consuming step, particularlywhen using singlemode fiber, and it is best performed by an automatedpolishing machine. Automated polishing machines are often large andexpensive, however, making them impractical for field use.

Fiber pigtail connectors were designed to eliminate the need for theselengthy steps. A pigtail connector is prepared at the factory with alength of fiber. In the factory, precise polishing machines can be usedto achieve a consistent polish. The endfaces can be inspected at thefactory to ensure correct endface geometry for optimum performance. Inthe field, the installer would have to splice a length of fiber to acable by means of a fusion splicing machine. This eliminates much of thelabor time, but it requires the installer to purchase a fusion splicingmachine and protective sleeve, which are expensive. This type ofconnector would require extra storage space for protection of the fusionsplice.

Fiber stub connectors were designed to eliminate the need for expensivefusion splicing equipment, splice protection, and lengthy terminationsteps. The stub connector employs a short fiber stub that is spliced tothe field fiber within the connector. Stub connectors typically requirea crimp to either activate the splice or retain the field fiber, orboth. The crimping operation, however, whether occurring at theinterface point or at some other point to retain the field fiber, mayhave a tendency to pull the field fiber and stub fiber apart, orotherwise damage the signal-passing function of the interface. If theconnection is found to be poor after the crimping occurs, the connectormust be cut off because crimping is generally an irreversible operation.Thus, the connector and a length of fiber optic cable are wasted, and anew connector must then be terminated. This waste can be expensive andtime-consuming, and can be an annoyance to the installer by delayingnetwork activation. A reusable stub connector would thus be desirable.

SUMMARY OF THE INVENTION

Described and claimed herein is a fiber optic connector that, in itspreferred embodiments, is completely reversible so that when a fieldfiber is unsuccessfully coupled to a stub fiber within a connector, oneor more subsequent attempts may be made to achieve a successful couplingusing the same connector and possibly even the same stripped end offiber. This saves time for the installer and avoids wasted fiber opticconnectors and other materials.

Among the most advantageous features of the inventive connectors and themethods by which they are used is the full reversibility of theconnection. While reversibly rotatable levers have previously been usedto effectuate and release an alignment in a fiber optic connector (suchas in EP1136860 A2), such connectors have not provided simultaneousbuffer clamping and disengagement. Thus, such connectors have generallyrequired an extra and irreversible (i.e., destructive) crimping of thebuffer to provide beneficial strain relief to the interface of thealigned field and stub fibers. Often such a crimping step may degradethe fiber interface, but since the crimp is irreversible, nothing can bedone to significantly improve the degraded connection short of cuttingaway the wasted connector, re-stripping and re-cleaving the fiber, andre-terminating the field fiber with a new stub fiber in a new connector.The need for this irreversible and destructive buffer crimp may beremoved by connectors in accordance with the invention, as is the needfor crimping more generally, while the beneficial strain relief is stillprovided.

In one embodiment of the invention, there is provided a fiber optic stubfiber connector for reversibly and nondestructively terminating aninserted field fiber having a buffer over a portion thereof. Theconnector includes a housing and a ferrule including a stub fiberdisposed within and extending from a bore extending through the ferrule.The ferrule is at least partially disposed within and supported by thehousing. The connector further includes a reversible actuator forreversibly and nondestructively terminating the inserted field fiber tothe stub fiber. The reversible actuator includes a buffer clamp forengaging with the buffer to simultaneously provide reversible andnondestructive strain relief to the terminated field fiber.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a front upper left perspective view of a connector inaccordance with a preferred SC embodiment of the invention;

FIG. 2 is a rear upper right perspective view of the connector of FIG.1;

FIG. 3 is an exploded view of the connector of FIG. 2;

FIG. 4 is an exploded view of the SC assembly shown in FIG. 3;

FIG. 4A is an enlarged perspective view of the buffer clamp of FIG. 4;

FIG. 5 is an exploded enlarged perspective view of a portion of the SCassembly of FIG. 4;

FIG. 6 is a front elevational view of the cam of FIG. 5;

FIG. 7 is an unexploded front lower right perspective view of theportion of the SC assembly shown in FIG. 5 other than the cam;

FIG. 8 is a top plan view of the SC assembly of FIG. 4 in an assembledcondition;

FIG. 9 is a right side elevational view of the SC assembly of FIG. 8;

FIG. 10 is a sectional perspective view of the SC assembly of FIG. 8;

FIG. 11 is a cross-sectional view of the SC assembly of FIG. 8 takenalong the line 11-11 in FIG. 8;

FIG. 12 is a cross-sectional view of the SC assembly of FIG. 9 takenalong the line 12-12 in FIG. 9;

FIG. 13 is a cross-sectional view of the SC assembly of FIG. 9 takenalong the line 13-13 in FIG. 9;

FIG. 14 is a cross-sectional view of the SC assembly of FIG. 9 takenalong the line 14-14 in FIG. 9;

FIG. 15 is a cross-sectional view of the SC assembly of FIG. 9 takenalong the line 15-15 in FIG. 9;

FIG. 16 is a front upper right perspective cross-sectional view of theSC assembly of FIG. 9 with the nut and boot attached;

FIG. 17 is a right side elevational cross-sectional view of the assemblyof FIG. 16;

FIG. 18 is a close-up broken-away view of a portion of the assembly ofFIG. 17;

FIG. 19 is a cross-sectional view of the assembly of FIG. 17 takenacross the line 19-19 in FIG. 18;

FIG. 20 is a cross-sectional view of the assembly of FIG. 17 takenacross the line 20-20 in FIG. 17;

FIG. 21 is a front upper right perspective view of a connector inaccordance with a preferred FJ jack embodiment of the invention;

FIG. 22 is a rear upper right perspective view of the connector of FIG.21;

FIG. 23 is an exploded view of the connector of FIG. 22;

FIG. 24 is an inverted view of the connector of FIG. 23;

FIG. 25 is a further exploded view of the connector of FIG. 23;

FIG. 26 is an exploded front lower right perspective view of theconnector of FIG. 21;

FIG. 27 is a top plan view of the connector of FIG. 21;

FIG. 28 is a right side elevational view of the connector of FIG. 27;

FIG. 29 is a cross-sectional view of the connector of FIG. 27 takenalong the line 29-29 in FIG. 27;

FIG. 30 is a cross-sectional view of the connector of FIG. 28 takenalong the line 30-30 in FIG. 28;

FIG. 31 is a cross-sectional view of the connector of FIG. 28 takenalong the line 31-31 in FIG. 28;

FIG. 32 is a cross-sectional view of the connector of FIG. 28 takenalong the line 32-32 in FIG. 28;

FIG. 33 is an exploded rear upper right perspective view of an FJassembly portion of the connector of FIG. 21;

FIG. 34 is a view of the assembly of FIG. 33 wherein one assembly hasbeen placed into an FJ cap;

FIG. 35 is a front upper left perspective view of the assembly of FIG.34;

FIG. 36 is a view akin to that of FIG. 24 wherein the assemblies havebeen placed within the FJ cap and are aligned with an FJ housing; and

FIG. 37 is a view akin to FIG. 36 wherein the connector is fullyassembled.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention relates generally to fiber optic connectors and moreparticularly to pre-polished fiber stub connectors.

As seen in perspective in FIGS. 1 and 2 and exploded FIG. 3, a preferredembodiment of a reversible and nondestructive fiber optic stub connector10 is used to terminate a field fiber. The connector 10 includes anouter housing 12 generally enclosing an SC assembly 13 with a backbone14. The field fiber 16 is inserted into the connector through thebackbone, and a boot/nut assembly having a boot 18 and retention nut 86overwraps and supports a cable jacket 19 and a buffer 20 surrounding thefiber 16. There may also preferably be Kevlar fibers 21 disposed betweenthe cable jacket and buffer, though in some embodiments the field fibermay only be buffered, with no cable jacket or Kevlar fibers.

As seen in FIGS. 4 and 5, the SC assembly has an inner housing 22containing a hollow ferrule holder 24 and a cam 26. The ferrule holderhas a ferrule-receiving portion 28 for surrounding one end of a ferrule30, a flange portion 32, a large barrel portion 34 having a rib slot 36,a medium barrel portion 38 having a clamp slot 40 for receiving a bufferclamp 41, and a small barrel portion 42 having an opening 44 at its end.The cam 26 includes a large barrel portion 46 having a lever 48extending outwardly therefrom, and a small barrel portion 50. There is alarge interior cam surface 52 within the large barrel portion 46 of thecam 26 and a small interior cam surface 53 within the small barrelportion 50 of the cam 26, the cam surfaces having variable radii fromthe center of the cam (the axis of the coaxial barrel portions of thecam). Although as seen in FIG. 6, the larger and smaller radii of therespective cam surfaces 52 and 53 are generally in angular alignment, itis not required that they be so aligned, and depending on the locationsand orientations of other connector components, there may be no suchalignment.

As can be further seen in these exploded figures, the shown embodimentof the connector includes a pair of planks, a clamp plank 54 and av-groove plank 56. The planks 54 and 56, which are inserted through theferrule receiving portion 28 and flange portion 32 of the ferrule holder24 and into the large barrel portion 34 thereof, cooperatively define agroove therebetween. In the shown embodiment, the groove 57 is generallypresent in the v-groove plank 56 and comes flush with a surface of theclamp plank 54 when the planks abut. Both ends of the planks preferablyhave tapered lead-in portions 58 to facilitate fibers being insertedinto the groove when the planks abut one another. The clamp plank 54includes a rib 55 extending outwardly therefrom for projecting throughthe rib slot 36 of the large barrel portion 34.

Once the planks are inserted into the large barrel portion of theferrule holder, the ferrule 30 and its associated stub fiber 60 areinserted into the ferrule-receiving portion 28 of the ferrule holder 24.The stub fiber 60 extends from the ferrule 30 into the front lead-inportions 58 and the groove 57 between the planks 54 and 56. The planksare generally flush against the ferrule 30, and while the front ends ofthe planks are generally near the interface between theferrule-receiving portion 28 and flange portion 32 of the ferrule holder24, the majority of the planks are disposed within the large barrelportion 34 thereof. The tapered lead-in portion 58 on the stub side ofthe planks prevents the preferably precision cleaved end of the stubfiber from being damaged if the fiber is not perfectly aligned with thegroove upon entry.

The buffer clamp 41, seen in detail in FIG. 4A, is preferably integraland includes a ring portion 62 and a stem portion 64. Partway along thelength of the stem, there is preferably disposed a transverse portion 66having a cam-following surface 68 at one end and a grasping portion 70at its opposite end. In a preferred embodiment of the invention, thegrasping portion is inclined to provide a lead-in for the fiber so thatthe buffer does not get caught thereon upon insertion. Also in apreferred embodiment, the grasping end includes teeth 71 that grip thebuffer through the clamp slot 40. The buffer clamp 41 is applied to theferrule holder 24 by circumscribing (i.e., clipping) the ring portion 62around the end of the small barrel portion 42 next to where it steps upto the medium barrel portion 38 such that the stem portion 64 fits intothe clamp slot 40 in the medium barrel portion 38.

The cam 26 is slid over the three barrel portions 34, 38, and 42 of theferrule holder 24 until it comes flush with the flange portion 32thereof. Given that the rib 55 of the upper crimp plank 54 protrudesthrough the rib slot 36 of the large barrel portion 34 and that thetransverse portion 66 and its cam following surface 68 of the bufferclamp 41 protrude from the clamp slot 40 of the medium barrel portion38, the cam 26 will have to be appropriately angularly oriented when itis being slid over the ferrule holder 24 so that the larger radii of therespective interior cam surfaces, 52 and 53, will fit over theseprotruding elements and not interfere with them such that the cam sleevecannot be applied over the ferrule holder.

The spring 72 fits over the outside of the small barrel portion 50 ofthe cam 26 and provides compressive resistance behind the ferrule sothat when the connector is mated to an appropriate port or otherconnector, good contact pressure between the respective ferrules or theferrule 30 and a contact point on the port may be achieved. The tabs 78on the barrel portion 76 are tapered to permit the backbone to bepressed into the aperture, such that the tapered tabs flex the splithousing apart during insertion and permit the housing to resilientlysnap back after the tabs have cleared. The tabs preferably retain thebackbone within the inner housing. The externally threaded portion 80,protrudes from the aperture 74.

The SC assembly 13 is preferably produced in the factory so that thefield operator who uses the connector to make a fiber optic connectionhas it preassembled. This limits the amount of assembly needed to beperformed in the field. To terminate a field fiber 16 with thepre-assembled connector, the cable jacket 19 is preferably stripped offa predetermined length of the buffer 20, as shown in FIG. 4. A retentionnut 86, preferably pre-assembled with the boot 18, is slid over the endof the field fiber 16 such that the fiber protrudes through the nut. Thebarrel portion 90 of the retention nut 86 is internally threaded so thatit may be screwed onto the externally threaded portion 80 of thebackbone 14 after the field fiber is terminated. The end of the fiber isthen preferably precision cleaved so that it will more cleanly engagethe stub fiber 60.

The field fiber is inserted through the externally threaded 80 portionof the backbone 14, through the small barrel portion 42 and mediumbarrel portion 38 and into the lead-in portions 58 and groove 57 of theplanks 54 and 56 within the large barrel portion 34 of the ferruleholder 24. The field fiber is inserted until its end contacts the end ofthe stub fiber 60 approximately half way over the length of the planksand approximately half way along the length of the rib 55 on the clampplank 54. Index-matching gel may preferably be supplied in the back halfof the groove to refractively limit signal loss at the interface of thefield fiber and stub fiber once the field fiber is appropriatelyaligned.

Once the operator determines that the fiber ends have made contact, hemanually rotates the lever 48 of the cam 26 that protrudes from an openportion of the inner housing 22. Rotation of the cam causes the largeinterior first cam surface 52 to tighten over the rib 55 that isprotruding through rib slot 36 in the large barrel portion 34 from clampplank 54. This causes the planks 54 and 56 to be squeezed together alongtheir abutting surfaces and the groove 57 therealong, therebycompressing the stub fiber end and field fiber end to hold them in placealong the length of the groove 57 and better align them to each otherwithin the groove at their interface. At the same time, the smallinterior second cam surface 53 tightens over the cam-following surface68 of the buffer clamp 41, thereby causing the grasping portion 70thereof to compress against the buffer 20, providing strain relief forthe field fiber and inhibiting any pulling of the stub and field fiberends away from one another within the groove. Additionally, the teeth 71of the buffer clamp inhibit rotational movement of the buffer layer andthe fiber inside. The cam 26 and the buffer clamp 41 comprise areversible actuator 43, as shown in FIG. 16.

Testing may be performed during the connection method by way of a localtesting device, such as a visible fault locator (VFL). Because noirreversible and/or destructive crimping, connecting or strain reliefmeasures are performed, if the testing indicates the fiber opticconnection, or even the mechanical connection, to be inadequate, theentire connective method is fully nondestructively reversible bymanually rotating the lever 48 of the cam 26 back into its originalposition. This simultaneously releases pressure on the rib 55 (andthereby the planks 54 and 56) and releases the compression of the bufferclamp 41 on the buffer. Thus, the field fiber may simply be rotated orotherwise agitated prior to reclamping the connector and once againdetermining whether a successful connection has been completed.Alternatively, the field fiber may be withdrawn from the connector atthat point, optionally recleaved, and subsequently reinserted foranother attempt at a successful connection. As with regard to other usesof the term “simultaneous” herein, actual chronological coincidence isnot required within the context of the invention, the term moregenerally referring to actions occurring around the same time and/orcaused by the same triggering event.

The front end 82 of the inner housing 22 is then inserted into the mouthof the outer housing 12, until the inner housing is completely swallowedby the outer housing and complementary structure on the outside of theinner housing and inside of the outer housing engages such that theinner housing is retained within the outer housing. The lever 48 of thecam 26 may preferably need to be rotated to a particular angularorientation to facilitate insertion of the ferrule holder 24 and cam 26into the inner housing 22 (to form the SC assembly 13), and thensubsequently to further facilitate the insertion of the SC assembly 13into the outer housing 12. The inner housing 22 preferably limitsrotation of the lever 48 where the cam is fully actuated. Once the SCassembly 13 is inserted into the outer housing 12, then, the lever 48will preferably be angularly fixed between the ferrule holder and outerhousing.

In summary then, the operator needs only to appropriately strip thefield fiber, insert it into the assembly, rotate the lever 48 of the cam26 to effect connection and strain relief at the buffer, verify theconnection with a local testing device, and then insert the assemblyinto the outer housing 12 and screw the retention nut 86 over theexternally threaded portion 80 of the backbone 14.

After successfully terminating the field fiber 16 with the pre-assembledstub-fiber connector, the connector can be inserted into anappropriately configured port in a patch panel or other device so thatthe preferably polished front face 84 of the ferrule 30 and similarlypolished front end of the stub fiber 60 may interface the device andpermit signals to pass from the field fiber to the device or vice-versa.

Among the most advantageous features of the inventive connectors and themethods by which they are used is the full reversibility of theconnection. While reversibly rotatable levers have previously been usedto effectuate and release an alignment in a fiber optic connector (suchas in EP1136860 A2), such connectors have not provided simultaneousbuffer clamping and disengagement. Thus, such connectors have generallyrequired an extra and irreversible (i.e., destructive) crimping of thebuffer to provide strain relief to the interface of the aligned fieldand stub fibers. Often such a crimping step may degrade the fiberinterface, but since the crimp is destructive, nothing can be done tosignificantly improve the degraded connection short of cutting away thewasted connector, re-stripping and re-cleaving the fiber, andre-terminating the field fiber with a new stub fiber in a new connector.The need for this irreversible and destructive buffer crimp may beremoved by connectors in accordance with the invention, as is the needfor crimping more generally.

It is contemplated within the scope of the invention that the reversibleactuator that may simultaneously align/terminate the fibers whileproviding strain relief on the buffer may essentially be two independentactuators, one for aligning/terminating the fibers and one for providingreversible and nondestructive strain relief on the buffer. While such anarrangement might involve an extra step in engaging the connector,depending upon whether the two actuations could both be toggled in asingle step, functionality or cost benefits could accrue from having thefunctions performed independently while preserving thenondestructiveness and full reversibility of the strain relief providedon the buffer. While the reversible actuator shown in the figures is acam, any type of reversible actuator, e.g., a switch, is considered tobe usable within the context of the invention.

The invention may be embodied in connectors differently formatted thanthe above disclosed SC-style optical plug, and FIGS. 21-37 show analternative embodiment of the invention, a connector generallyconfigured to be an FJ-style optical jack. It is possible to employ theinvention within other formats, however, such as plugs or jacksconformed to the SC, LC, ST, or FJ standards.

The FJ jack 110 of FIGS. 21-37, as seen in FIGS. 25 and 26 particularly,essentially employs two SC assemblies identical to the one describedabove for the SC-style plug connector with additional components tomatch the FJ standard. With equivalent pieces of the FJ embodimentnumbered 100 more than their corresponding parts in the SC connector,the two assemblies 113 are placed side-by-side into an FJ cap 190. Thetwo ferrules 130 are circumscribed by split sleeves 191 that are held inplace by split sleeve retainers 192. The ferrules and attached splitsleeves are fitted into ferrule openings 193 in an FJ housing 194. Theretainers 192 may preferably include tabs 195 for fitting into grooves196 in the ferrule openings 193. A front edge 197 of the cap 190, whichfits over the assemblies 113, will generally preferably come flush witha rear portion 198 of the FJ housing 194 when the split sleeve-encircledferrules 130 are fully inserted into the openings 193. The FJ housing194 includes a recessed front portion 199 providing access to thepreferably polished front faces 184 of the ferrules 130 for receivingand mating with a correspondingly configured FJ-plug type connector orother compatible connector. The front ends 182 of the inner housings 122may include less latching structure than in the SC embodiment(s) sincethe FJ cap 190 and housing 194 replace the need for latching to an outerhousing, such as outer housing 12. Other latching on the cap and housingmay be used to facilitate retention. Ribs 189 may preferably be placedon the cap to facilitate manually gripping the cap and connector.

The FJ jack embodiment of the invention retains the full reversibilityadvantages described relative to the SC plug embodiment, as each of thetwo fiber optic connections is fully reversible by rotating lever 148.Additionally, given their side-by-side placement within the FJ cap andhousing, the rotation and angular placement of the levers 148 on thecams may be advantageously located such that only when the levers arerotated to a closed position (i.e., aligned fibers) may the assembliesbe inserted into the cap and housing. Another advantage of the FJ-jack110 is that the ferrules 130 may float on the springs 172 to providecontact pressure when the jack engages a plug or other connectivehardware.

The illustrated and above-described embodiments of the invention areexemplary only and are not intended to limit the scope of protection inany way. To the contrary, the invention is considered to includeembodiments not specifically shown or described herein. For example, abuffer clamp having a grasping portion structurally different than theone shown in FIG. 4A would nevertheless be considered to be within thescope of the invention. Similarly, a buffer clamp that engaged thebuffer in a different manner to provide strain relief would also beconsidered to be within the scope of the invention. Also, a buffer neednot include any particular type of material, and circumscribingmaterials of different types may be alternatively present in accordancewith various embodiments of the invention. Additionally, the inventionis not limited to the particular SC and FJ optical formats described andillustrated herein, as the invention could be employed in other opticalformats currently or not yet existing. Similarly, the invention could beemployed in a plug-like or jack/receptor-like connector, as themale/female structure generally does not prevent use of the invention.The invention is defined by the following claims.

1. A ferrule holder assembly for a fiber optic connector comprising: aferrule receiving portion; at least three barrel portions havingprogressively smaller outer radii, said barrel portions comprising alarge barrel portion, a medium barrel portion, and a small barrelportion wherein said large barrel portion is provided with a rib slotand said medium barrel portion is provided with a clamp slot; and aclamp having a stem portion that fits into said clamp slot of saidmedium barrel portion, and a grasping portion adapted to pass throughsaid clamp slot and grasp a portion of an optical fiber located withinsaid medium barrel portion.
 2. The ferrule holder of claim 1 furthercomprising a flange portion positioned on an outside surface of saidferrule holder between said ferrule receiving portion and said largebarrel portion.
 3. The ferrule holder of claim 1 wherein said largebarrel portion is positioned to receive planks of said fiber opticconnector.
 4. The ferrule holder of claim 1 wherein said rib slot passescompletely through from an inside of the ferrule holder to an outside ofthe ferrule holder.
 5. The ferrule holder of claim 3 wherein said ribslot accepts a rib extending from one of said planks.